Summary of Significant Accounting Policies and Basis of Presentation (Policy)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Fiscal Period	Significant Accounting Policies We have prepared our consolidated financial statements using the accounting policies described in our Annual Report on Form 10-K for the year ended December 31, 2016.
New Accounting Pronouncements	Pronouncements Not Yet Adopted In August 2017, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) 2017-12, Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities. The purpose of this updated guidance is to better align a company’s financial reporting for hedging activities with the economic objectives of those activities. The transition guidance provides companies with the option of early adopting the new standard using a modified retrospective transition method in any interim period after issuance of the update, or alternatively requires adoption for fiscal years beginning after December 15, 2018. This adoption method will require us to recognize the cumulative effect of initially applying the ASU, if any, as an adjustment to accumulated other comprehensive income with a corresponding adjustment to the opening balance of retained earnings as of the beginning of the fiscal year that an entity adopts the update. While we continue to assess all potential impacts of the standard, we do not expect adoption to have a material impact on our consolidated financial statements. In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718) - Scope of Modification Accounting, which provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The new standard is effective for all entities for fiscal years beginning after December 15, 2017 and for interim periods therein. Early adoption is permitted. We do not expect the new standard to have a material impact on our consolidated financial statements. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230) - Restricted Cash, which requires that restricted cash and cash equivalents be included with cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts shown on the consolidated statements of cash flows. The new standard is effective for public entities for fiscal years beginning after December 15, 2017 and for interim periods therein, with early adoption permitted. We are currently evaluating the impact the new standard may have on Washington REIT’s consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments, which provides specific guidance on how cash receipts and payments should be presented and classified in the statement of cash flows for eight specific issues. The new standard is effective for public entities for fiscal years beginning after December 15, 2017 and for interim periods therein, with early adoption permitted. We are currently evaluating the impact the new standard may have on Washington REIT’s consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments, which requires financial assets measured at an amortized cost basis, including trade receivables, to be presented at the net amount expected to be collected. The new standard is effective for public entities for fiscal years beginning after December 15, 2019 and for interim periods therein with adoption one year earlier permitted. We are currently evaluating the impact the new standard may have on Washington REIT’s consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”), which amends existing accounting standards for lease accounting, including by requiring lessees to recognize most leases on the balance sheet and making certain changes to lessor accounting. The new standard is effective for public entities for fiscal years beginning after December 15, 2018 and for interim periods therein with early adoption permitted. Upon adoption, for leases in which we are the lessor, the lease contract will be separated into lease and non-lease components in accordance with the provisions outlined within ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”). The lease component of the contract will be recognized on a straight-line basis in accordance with ASU 2016-02, while the non-lease component will be recognized under the provisions of ASU 2014-09. For lease contracts with a duration of more than one year in which we are the lessee, the present value of future lease payments will be recognized on our balance sheet as a right-of-use asset and a corresponding lease liability. Also, only direct leasing costs may be capitalized under the new standard, while current accounting standards allow for the capitalization of indirect leasing costs. We are currently evaluating the impact ASU 2016-02 may have on Washington REIT’s consolidated financial statements. In June 2014, the FASB issued ASU 2014-09, which creates a single source of revenue guidance. The new standard provides accounting guidance for all revenue arising from contracts with customers and affects all entities that enter into contracts to provide goods or services to their customers (unless the contracts are in the scope of other U.S. generally accepted accounting principles (“GAAP”) requirements, such as the leasing literature). The guidance also provides a model for the measurement and recognition of gains and losses on the sale of certain nonfinancial assets, such as property and equipment, including real estate. The new standard is effective for public entities for fiscal years beginning after December 15, 2017 and for interim periods therein. Early adoption is permitted for public entities beginning after December 15, 2016. We intend to adopt the new standard using the modified retrospective method. Upon adoption of ASU 2016-02, the majority of our revenue will be subject to the allocation provisions outlined within the revenue standard. We are currently evaluating the specific implementation requirements for allocating the consideration within our contracts in accordance with ASU 2014-09. We do not expect the new standard to have a material impact on the measurement and recognition of gains and losses on the sale of properties.
Principles of Consolidation and Basis of Presentation	Principles of Consolidation and Basis of Presentation The accompanying unaudited consolidated financial statements include the consolidated accounts of Washington REIT, our majority-owned subsidiaries and entities in which Washington REIT has a controlling interest, including where Washington REIT has been determined to be a primary beneficiary of a variable interest entity (“VIE”). See note 3 for additional information on the property for which there is a noncontrolling interest. All intercompany balances and transactions have been eliminated in consolidation.
Basis of Accounting	We have prepared the accompanying unaudited financial statements pursuant to the rules and regulations of the Securities and Exchange Commission “SEC”). Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations, although we believe that the disclosures made are adequate to make the information presented not misleading. In addition, in the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation of the results for the periods presented have been included. These unaudited financial statements should be read in conjunction with the financial statements and notes included in our Annual Report on Form 10-K for the year ended December 31, 2016. Within these notes to the financial statements, we refer to the three months ended September 30, 2017 and September 30, 2016 as the “2017 Quarter” and the “2016 Quarter,” respectively and the nine months ended September 30, 2017 and September 30, 2016 as the "2017 Period" and "2016 Period," respectively
Use of Estimates in the Financial Statements	Use of Estimates in the Financial Statements The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.